The invention is directed to a method and apparatus for the manufacture of optical cables wherein at least one light waveguide is introduced with excess length into at least one chamber proceeding in the fashion of a helical line in a center element and a filling compound is introduced into the chamber.
U.S. Pat. No. 4,199,224, whose disclosure is incorporated by reference thereto and which claimed priority from German Application No. 24 49 439, discloses a method for providing light waveguides in a chambered cable. As disclosed, a core of the cable has outwardly opening chambers which receive light waveguides. The details concerning the manner by which the filling compound is introduced into the respective chambers is not set forth in this prior art reference. It is merely set forth that with respect to the light waveguides that these are to be introduced in a pushing fashion into the chambers provided for their acceptance.
German Patent No. 30 27 743 discloses a method wherein one or more light waveguides are loosely introduced into an outside protective sheath which is produced by an extruder. The light waveguides are conducted through a tube which is arranged after a constrained conveying means. The tube extends through a passage opening provided in the extruder which opening roughly exits the location of the extrusion head for the outer sheath A strain can be produced with hydraulic drag mechanism through which the light waveguide is moved with a filling compound flowing in the tube. The cables manufactured in accordance with this patent are of a design that is different fundamentally from those of the "chambered cables" because the light waveguide or light waveguides in the "chambered cables" are laid into outwardly opening chambers, whereas the light waveguides of this German patent are arranged loosely in a closed tubular protective sheath.
European Patent No. 0 132 446 discloses that haul-offs are provided in a chambered cable for the central element that contains the chambers The haul-off speeds of these haul-offs are matched to one another so that the central element is stretched between the two haul-offs during the insertion of the light waveguides and the degree of stretching is in the elastic region or range of the central element. An excess length for the light waveguides occurs due to the following spring back of the central element when the stretching forces are released
U.S. Pat. No. 4,548,664, whose disclosure is incorporated herein by reference thereto and which claims priority from the same application as European Patent No. 0 132 827, discloses the chambers of a core proceeding in the fashion of a helical line and are completely filled with a viscous filling material in a separate operating cycle. As disclosed, the fibers are laid in the chambers and then wrapped loosely with a first tape which is provided with gaps between turns. This wrapped element is then passed through an injection device by which the filling material is injected through the gaps between the turns of the tape to fill each of the chambers and subsequently a second tape is wrapped on the element to close the gaps. The steps of insertion of the fibers and insertion of the filling compound are two separate steps as disclosed by this patent.
SUMMARY OF THE INVENTION
The object of the present invention is to execute the insertion of the light waveguides and the filling process in an optimally simple way and to simultaneously guarantee that the light waveguides are introduced in the chambers without a great outlay and in a gentle fashion. In accordance with this invention, this is achieved by a method which requires moving a core having a chamber, and then inserting the fiber and filling compound simultaneously in one working step into this chamber.
The two separate work steps are thus no longer required for the introduction of the filling compound on the one hand and for the introduction of the light waveguide on the other hand. Instead, both are carried out in common. With respect to the light waveguide, this additionally has the advantage that they can be introduced into the respective chambers in an especially gentle way because the light waveguides are already embedded in the filling compound during the filling and introduction step and this practically completely eliminates the mechanical stressing of the light waveguide during the introduction step. The filling compound itself is thus simultaneously used as a soft cushioning guidance for the light waveguide.
The invention is also directed to an apparatus for the implementation of the method set forth above. This apparatus is characterized in that the filling and introduction means is provided that comprises a common guide tube for both the light waveguide and the filling compound
Other advantages and features of the invention will be readily apparent from the following description of the preferred embodiments, the drawings and claims.